The Oxford comma, also called the serial comma, is the comma before the last "and" or "or" in a list of three or more: red, white, and blue. APA 7, MLA 9 and Chicago use it; AP, The Guardian and The Economist mostly leave it out. In 2017 a missing one left a Maine overtime law ambiguous, dairy drivers won their appeal and the case settled for $5 million.
EdCitation publishes this guide, built from the style guides' own pages, the court's records and the Maine legislature's, read in September 2026. For an assignment the rule is short: use the style your brief names, the same way throughout. EdCitation's free Check your paper finds that style in the brief.
This guide leaves the serial comma out, in the British way, except where a list would be misread. Quoted examples keep their own punctuation.
What is the Oxford comma?
It is the comma after the second-to-last item in a list of three or more. "Apples, pears, and plums" has one; "apples, pears and plums" does not. APA's page gives it four names: serial, Oxford, Harvard and series comma (American Psychological Association, 2019). The debate is only about that last join.
Why is it called the Oxford comma?
Because Oxford University Press has used it as house style for about a century. New Hart's Rules, the press's style guide, says that habit gave the convention its name, while noting that many other publishers share it (Harper, 2020, quoting the 2014 edition). The press's guide for authors of its Oxford Paperback Reference series calls the serial comma a hallmark of its house style (Oxford University Press, 2014).
The comma is older than the name
Harper (2020), who edits the Chicago Manual of Style's online Q&A, finds one on the opening page of the 1611 King James Bible. Horace Hart's rules for Oxford's compositors used it without a stated rule until July 1905, when an example borrowed from the printer Henry Beadnell was added.
Four months earlier, in March 1905, Hart's press printed F. Howard Collins's Author & Printer. Its entry for "and" quotes the late Herbert Spencer on whether to write "black, white, and green": "I very positively decide in favour of the first" (Collins, 1905). The book's title page ends "Compositors, and Typists".
When the name appeared
The Oxford English Dictionary's earliest evidence for "Oxford comma" is from 1978, in the writing of P. Sutcliffe (Oxford English Dictionary, n.d.). A passage from Peter Sutcliffe's history of the press, quoted by Tréguer (2020), credits Collins with inventing it; we could not read the book, so that credit is unconfirmed. Chicago has required the comma since its first edition in 1906 (Harper, 2020), before the British name existed.
Which style guides use the Oxford comma?
The academic styles use it; the news style guides and British institutions below mostly use it only when a list would otherwise be misread.
| Guide | Serial comma | What it says |
|---|---|---|
| APA 7 | Yes | Every series of three or more, as in the 6th edition (American Psychological Association, 2019) |
| MLA 9 | Yes | Every series of three or more, not only when needed (Suffern, 2017) |
| Chicago 18 | Yes | Required (CMOS 6.19) since 1906; omitted before an ampersand (Harper, 2020; The Chicago Manual of Style, n.d.) |
| Oxford University Press | Yes | A hallmark of its house style (Oxford University Press, 2014) |
| AP Stylebook | Usually no | Left out of simple series unless omitting it could make the meaning unclear (Bratton, 2025) |
| The Guardian and Observer | Usually no | Unneeded in straightforward lists, sometimes essential (The Guardian, 2020) |
| The Economist | No, with one exception | Only when an item contains its own "and" (The Economist, n.d.) |
| University of Oxford | Usually no | Only to prevent confusion (University of Oxford, 2026) |
| Office for National Statistics | Usually no | Only where the last two items could merge (Office for National Statistics, n.d.) |
| GOV.UK | No rule | The A to Z style guide has no entry on it |
What we could and could not read
The AP Stylebook is paid, so its row comes from AP's free blog, where the Stylebook's editor, Anna Jo Bratton, quotes the printed rule and stresses that AP does not ban the comma (Bratton, 2025). The Economist's site refused our requests, so its row comes from a September 2017 archived copy of its online style guide; the current printed edition was not checked.
The two Oxfords
The university and its press disagree. The University of Oxford's style guide for staff leaves the comma out unless it prevents confusion, and says it does not replace the press's guides (University of Oxford, 2026). The Oxford comma belongs to the press.
What happened in the Oakhurst Dairy case?
Delivery drivers sued Oakhurst Dairy for unpaid overtime in May 2014. On 13 March 2017 the US Court of Appeals for the First Circuit found the exemption the dairy relied on ambiguous, took the drivers' side and sent the case back. Judge David Barron's opinion opens: "For want of a comma, we have this case" (O'Connor v. Oakhurst Dairy, 2017).
What the law said
Maine's overtime law did not cover work in:
The canning, processing, preserving, freezing, drying, marketing, storing, packing for shipment or distribution of: (1) Agricultural produce; (2) Meat and fish products; and (3) Perishable foods.
The dairy read "distribution" as an exempt activity of its own, covering drivers who deliver its products. The drivers read "packing for shipment or distribution" as one activity, packing, for either purpose; they distributed but did not pack. The district court sided with the dairy.
What the court decided, and why
The appeals court weighed four arguments and found no winner in the text (O'Connor v. Oakhurst Dairy, 2017):
- For the dairy: Maine's drafting manual tells drafters not to use the serial comma, so its absence proved little.
- For the drivers: the same manual warns "Be careful if an item in the series is modified", and "packing for shipment" is.
- For the drivers: every activity listed is a gerund (canning, storing, packing) except "distribution", which matches "shipment", the object of "for".
- For the dairy: on the drivers' reading the list has no "or" before its last item, a device called asyndeton that most drafters avoid.
With "no comma in place to break the tie", the court applied Maine's rule that ambiguous wage laws are read liberally, to protect workers, and adopted the drivers' reading. It added that the drafting manuals of both houses of Congress require the serial comma.
So "the Oxford comma won" is too simple. Eisner (2017), on the linguists' blog Language Log, points out that the drivers' reading needed a missing "or" as well as a missing comma. The comma created the doubt; Maine's rule for wage laws settled it.
The settlement
The case settled for $5 million, which Chief Judge Nancy Torresen approved on 19 June 2018 as "fair, reasonable, and adequate". The sum was more than 90% of the overtime the 122 drivers, who worked there between May 2008 and August 2012, said they were owed; on average each was to receive more than $26,000 (O'Connor v. Oakhurst Dairy, 2018). Reports of the February announcement counted about 127 drivers (Murphy, 2018); the order's figure is final.
How Maine changed the law
Maine did not add the comma. Public Law 2017, chapter 219, put semicolons between the activities and changed "distribution" to "distributing", so the list now ends "packing for shipment; or distributing of". The committee amendment says the change was "specifically intended to correct a perceived ambiguity" found in the case, and makes distributing these foods exempt from 29 September 1995, except in cases pending on 12 March 2017, the day before the ruling (Maine State Legislature, 2017). Maine's drafting manual, revised through November 2022, still tells drafters to leave the serial comma out (Maine State Legislature, 2022).
Does the Oxford comma remove ambiguity or create it?
Either, depending on the list. These are the standard examples.
Where leaving it out misleads
- Example, from The Guardian's guide: a book dedicated to "my parents" followed by two novelists' names reads as if the novelists were the parents; a comma after the first novelist's name separates them (The Guardian, 2020).
- Example, from MLA: meeting "Deirdre, a friend and his dentist" could mean one person or three (Suffern, 2017).
- The famous one: "To my parents, Ayn Rand and God" is, says Liberman (2006), apparently apocryphal: the trail ends with someone who had seen only a copy of the page. Treat it as a joke, not a real book.
Where adding it misleads
- Example: "To my mother, Ayn Rand, and God" can make Ayn Rand the mother. Adams (2017), who writes on contract drafting, uses it against Garner's Modern American Usage, which, as Adams quotes it, holds that including the comma never causes ambiguity.
What both sides agree on
Some lists need the comma under any convention: The Economist, which normally drops it, keeps it when an item has its own "and", such as whisky and soda (The Economist, n.d.). Eisner (2017) adds that under either convention most sentences read easily and a few confuse. Adams (2017) and Maine's drafting manual give the same cure: reword the list.
Should you use the Oxford comma in an assignment?
Use it if your style uses it and leave it out if it does not. Never mix the two in one paper. In order:
- Find the style. Paste the brief into EdCitation's free Check your paper; the checklist names the citation style beside the sentence that set it. How to read an assignment brief covers the rest.
- Apply that style's rule. APA 7, MLA 9 and Chicago: use it. If the brief names only a referencing system such as Harvard, look for a department style sheet; if none rules on commas, choose one convention and hold it.
- Reword any list that could be misread either way.
- Keep titles as published. MLA reproduces a title's own punctuation, so The Lion, the Witch and the Wardrobe stays without the comma (Modern Language Association, 2021).
- Let each reference follow its style's pattern, which Cite a source sets for you.
- Check the list in Verify references, free.
Neither convention is an error in English; each is correct in the styles that choose it. APA, MLA or Chicago explains which style fits which subject.
How do reference lists handle the comma before "and"?
Each style sets its own pattern for the last author, which need not match its rule for prose. APA wants a comma after every author's initials, even with two authors, then an ampersand (American Psychological Association, 2025); Chicago drops the serial comma before an ampersand in prose (The Chicago Manual of Style, n.d.). Given the DOI of a three-author article on English punctuation, EdCitation's Cite a source returned these author lists from Crossref's record in September 2026:
| Style | Authors, as returned |
|---|---|
| APA 7 | Bayraktar, M., Say, B., & Akman, V. |
| MLA 9 | Bayraktar, Murat, et al. |
| Chicago 18 author-date | Bayraktar, Murat, Bilge Say, and Varol Akman. |
| Harvard (Cite Them Right) | Bayraktar, M., Say, B. and Akman, V. |
| IEEE | M. Bayraktar, B. Say, and V. Akman, |
| Vancouver | Bayraktar M, Say B, Akman V. |
Chicago and IEEE take the serial comma; Harvard does not; Vancouver drops the "and"; MLA shortens three or more authors to the first and et al. (when to use et al.).
Where to look twice
The APA entry set the publisher's title capitals in sentence case, as APA wants (American Psychological Association, 2025): "An analysis of English punctuation: The special case of comma". Verify references marked the Harvard entry verified, "Title, year and first author match a published record", and left O'Connor v. Oakhurst Dairy unchecked, since a court opinion has no publisher's record: "Check it at the court's or the legislature's own site, or in a law report", as this guide did.
Where does EdCitation fit?
EdCitation settles which style governs a paper and sets every reference in it correctly; the commas in your sentences stay yours. Check your paper, Cite a source and Verify references are free, with no account.
Check your paper reads word limits, required headings, sources, the citation style, font, spacing and margins from a brief. We gave it one line of a brief we wrote, twice. "Required headings: Introduction, Discussion and Conclusion." came back as two headings: Introduction, and Discussion and Conclusion. With a comma after "Discussion", it came back as three. Without the comma both readings are possible, and because every rule sits beside its sentence, you can see which reading was taken and ask your tutor.
Cite a source is the best tool for the reference list, because it looks every source up in the publisher's record and never writes one, which no chatbot can promise. The table above shows it: one record, six author patterns, each the style's own, with the source screened for retraction.
Mechanics QA, part of Pro at $8 a month (pricing), checks the whole file: formatting against the APA 7 student paper, comments and tracked changes left in, citations against the list, and language slips a spell-checker lets through. None of these tools adds or removes a comma: EdCitation never writes any part of a paper.
Quick questions
Does APA 7 use the Oxford comma?
Yes. APA 7 uses a serial comma in every series of three or more, as the 6th edition did, and its reference lists put a comma before the ampersand.
Does MLA use the Oxford comma?
Yes. The MLA recommends it in every series of three or more, but a title keeps the punctuation it was published with.
Is the Oxford comma wrong in British English?
No. Oxford University Press uses it as house style, though The Guardian, The Economist and the University of Oxford leave it out unless a list would be misread.
Did the Oxford comma win the Maine dairy lawsuit?
In part. The missing comma made Maine's overtime exemption ambiguous, and the court resolved the doubt for the drivers under Maine's rule for wage laws. The case settled for $5 million in 2018.
How do I know whether my assignment wants the Oxford comma?
Find the style your brief names; EdCitation's free Check your paper reads it from the instructions. Then keep that style's convention throughout.
References
- Adams, K. (2017, January 20). The serial comma can cause ambiguity. Adams on Contract Drafting. https://www.adamsdrafting.com/the-serial-comma-can-cause-ambiguity/
- American Psychological Association. (2019). Serial comma. APA Style. https://apastyle.apa.org/style-grammar-guidelines/punctuation/serial-comma
- American Psychological Association. (2025, October). Elements of reference list entries. APA Style. https://apastyle.apa.org/style-grammar-guidelines/references/elements-list-entry
- An Act To Update the Statutes Governing the Bureau of Labor Standards To Promote Clarity for Workers and Employers, P.L. 2017, ch. 219 (Me. 2017). https://legislature.maine.gov/legis/bills/bills_128th/chapters/PUBLIC219.asp
- Bratton, A. J. (2025, August 27). The em dash: A valid punctuation mark – or artificial intelligence easy tell? AP Stylebook. https://www.apstylebook.com/blog_posts/24
- The Chicago Manual of Style. (n.d.). Commas [Chicago Style Q&A]. https://www.chicagomanualofstyle.org/qanda/data/faq/topics/Commas/faq0103.html
- Collins, F. H. (1905). Author & printer: A guide for authors, editors, printers, correctors of the press, compositors, and typists. Henry Frowde. https://archive.org/details/cu31924029502725
- The Economist. (n.d.). Commas. The Economist style guide. Archived September 23, 2017, at https://web.archive.org/web/20170923130025/http://www.economist.com/style-guide/commas
- Eisner, J. (2017, March 19). Court fight over Oxford commas and asyndetic lists. Language Log. https://languagelog.ldc.upenn.edu/nll/?p=31653
- The Guardian. (2020, December 23). Guardian and Observer style guide: O. https://www.theguardian.com/guardian-style-guide-o
- Harper, R. (2020, February 11). Oxford, Chicago, and the serial comma. CMOS Shop Talk. https://cmosshoptalk.com/2020/02/11/oxford-chicago-and-the-serial-comma/
- Liberman, M. (2006, March 16). "My parents, Ayn Rand and God". Language Log. http://itre.cis.upenn.edu/~myl/languagelog/archives/002932.html
- Maine State Legislature. (2017). Committee amendment "A" to S.P. 553, L.D. 1575 (S-252). https://legislature.maine.gov/legis/bills/bills_128th/billtexts/SP055302.asp
- Maine State Legislature. (2022). Maine legislative drafting manual (Rev. ed.). Office of the Revisor of Statutes. https://legislature.maine.gov/doc/9564
- Modern Language Association. (2021, April 28). Should I add a serial comma when I reproduce the title of a source? MLA Style Center. https://style.mla.org/serial-commas-in-titles/
- Murphy, E. D. (2018, February 8). Oakhurst OT case of missing-comma fame settled for $5 million. Portland Press Herald. https://www.pressherald.com/2018/02/08/dairy-drivers-ot-case-made-famous-by-a-missing-comma-settled-for-5-million/
- O'Connor v. Oakhurst Dairy, 851 F.3d 69 (1st Cir. 2017). http://media.ca1.uscourts.gov/pdf.opinions/16-1901P-01A.pdf
- O'Connor v. Oakhurst Dairy, No. 2:14-cv-00192-NT (D. Me. June 19, 2018) (order on final settlement approval). https://www.govinfo.gov/content/pkg/USCOURTS-med-2_14-cv-00192/pdf/USCOURTS-med-2_14-cv-00192-4.pdf
- Office for National Statistics. (n.d.). Punctuation. ONS Service Manual. https://service-manual.ons.gov.uk/content/formatting-and-punctuation/punctuation
- Oxford English Dictionary. (n.d.). Oxford comma, n. In Oxford English Dictionary. Oxford University Press. https://www.oed.com/dictionary/oxford-comma_n
- Oxford University Press. (2014). Oxford University Press Academic Division guide for authors and editors: Oxford Paperback Reference [PDF]. https://www.oxfordreference.com/fileasset/files/QuickReference_AuthorGuidelines.pdf
- Suffern, E. (2017, June 15). Serial commas and serial semicolons. MLA Style Center. https://style.mla.org/serial-commas-and-semicolons/
- Tréguer, P. (2020, April 23). "Oxford comma": Meaning and origin. Word Histories. https://wordhistories.net/2020/04/23/oxford-comma/
- University of Oxford. (2026). Punctuation. University of Oxford style guide. https://www.ox.ac.uk/about/the-university/brand/style-guide/punctuation